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LYME DISEASE

Lyme disease was first recognized in the United States in 1975, after a
mysterious outbreak of arthritis near Lyme, Connecticut. Since then,
reports of Lyme disease have increased dramatically, and the disease has
become an important public health problem in some areas of the United
States.

Lyme disease is an infection caused by Borrelia burgdorferi, a member
of the family of spirochetes, or corkscrew-shaped bacteria.

How the disease is spread

Lyme disease is spread by the bite of ticks of the genus Ixodes that
are infected with Borrelia burgdorferi. The deer (or bear) tick, Ixodes
dammini, which normally feeds on the white-footed mouse, the white-tailed
deer, other mammals, and birds, is responsible for transmitting Lyme
disease bacteria to humans in the northeastern and north-central United
States. (In these regions, this tick is also responsible for the spreading
of babesiosis, a disease caused by a malaria-like parasite.) On the Pacific
Coast, the bacteria are transmitted to humans by the western black-legged
tick, Ixodes pacificus, and in the southeastern states possibly by the
black-legged tick, Ixodes scapularis.

Ixodes ticks are much smaller than common dog and cattle ticks. In
their larval and nymphal stages, they are no bigger than a pinhead. Adult
ticks are slightly larger.

Ticks can attach to any part of the human body but often attach to the
more hidden and hairy areas such as the groin, armpits, and scalp.

Research in the eastern United States has indicated that, for the most
part, ticks transmit Lyme disease to humans during the nymph stage,
probably because nymphs are more likely to feed on a person and are rarely
noticed because of their small size (less than 2 mm). Thus, the nymphs
typically have ample time to feed and transmit the infection (ticks are
most likely to transmit infection after approximately 2 or more days of
feeding).

Tick larvae are smaller than the nymphs, but they rarely carry the
infection at the time of feeding and are probably not important in the
transmission of Lyme disease to humans.

Adult ticks can transmit the disease, but since they are larger and
more likely to be removed from a person's body within a few hours, they are
less likely than the nymphs to have sufficient time to transmit the
infection. Moreover, adult Ixodes ticks are most active during the cooler
months of the year, when outdoor activity is limited.

Ticks search for host animals from the tips of grasses and shrubs (not
from trees) and transfer to animals or persons that brush against
vegetation. Ticks only crawl; they do not fly or jump. Ticks found on the
scalp usually have crawled there from lower parts of the body. Ticks feed
on blood by inserting their mouth parts (not their whole bodies) into the
skin of a host animal. They are slow feeders: a complete blood meal can
take several days. As they feed, their bodies slowly enlarge.

Although in theory Lyme disease could spread through blood transfusions
or other contact with infected blood or urine, no such transmission has
been documented. There is no evidence that a person can get Lyme disease
from the air, food or water, from sexual contact, or directly from wild or
domestic animals. There is no convincing evidence that Lyme disease can be
transmitted by insects such as mosquitoes, flies, or fleas.

Campers, hikers, outdoor workers, and others who frequent wooded,
brushy, and grassy places are commonly exposed to ticks, and this may be
important in the transmission of Lyme disease in some areas. Because new
homes are often built in wooded areas, transmission of Lyme disease near
homes has become an important problem in some areas of the United States.
The risk of exposure to ticks is greatest in the woods and garden fringe
areas of properties, but ticks may also be carried by animals into lawns
and gardens.

Geographic distribution

Lyme disease has a wide distribution in northern temperate regions of
the world. In the United States, the highest incidence occurs in the

Northeast, from Massachusetts to Maryland.

North-central states, especially Wisconsin and Minnesota.

West Coast, particularly northern California.

For Lyme disease to exist in an area, at least three closely
interrelated elements must be present in nature: the Lyme disease bacteria,
ticks that can transmit them, and mammals (such as mice and deer) to
provide food for the ticks in their various life stages. Ticks that
transmit Lyme disease can be found in temperate regions that may have
periods of very low or high temperature and a constant high relative
humidity at ground level.

Life cycle of Lyme disease ticks

Knowing the complex life cycle of the ticks that transmit Lyme disease
is important in understanding the risk of acquiring the disease and in
finding ways to prevent it.

The life cycle of these ticks requires 2 years to complete. Adult ticks
feed and mate on large animals, especially deer, in the fall and early
spring. Female ticks then drop off these animals to lay eggs on the ground.
By summer, eggs hatch into larvae.

Larvae feed on mice and other small mammals and birds in the summer and
early fall and then are inactive until the next spring when they molt into
nymphs.

Nymphs feed on small rodents and other small mammals and birds in the
late spring and summer and molt into adults in the fall, completing the
2-year life cycle.

Larvae and nymphs typically become infected with Lyme disease bacteria
when they feed on infected small animals, particularly the white-footed
mouse. The bacteria remain in the tick as it changes from larva to nymph or
from nymph to adult. Infected nymphs and adult ticks then bite and transmit
Lyme disease bacteria to other small rodents, other animals, and humans,
all in the course of their normal feeding behavior.

Lyme disease in domestic animals

Domestic animals may become infected with Lyme disease bacteria and
some of these (dogs, for instance) may develop arthritis. Domestic animals
can carry infected ticks into areas where humans live, but whether pet
owners are more likely than others to get Lyme disease is unknown.

Symptoms and signs of Lyme disease

Early Lyme Disease: The early stage of Lyme disease is usually marked
by one or more of the following symptoms and signs:

fatigue

chills and fever

headache

muscle and joint pain

swollen lymph nodes

a characteristic skin rash, called erythema migrans

Erythema migrans is a red circular patch that appears usually 3 days to
1 month after the bite of an infected tick at the site of the bite. The
patch then expands, often to a large size. Sometimes many patches appear,
varying in shape, depending on their location. Common sites are the thigh,
groin, trunk, and the armpits. The center of the rash may clear as it
enlarges, resulting in a bulls-eye appearance. The rash may be warm, but it
usually is not painful. Not all rashes that occur at the site of a tick
bite are due to Lyme disease, however. For example, an allergic reaction to
tick saliva often occurs at the site of a tick bite. The resulting rash can
be confused with the rash of Lyme disease. Allergic reactions to tick
saliva usually occur within hours to a few days after the tick bite,
usually do not expand, and disappear within a few days.

Late Lyme Disease: Some symptoms and signs of Lyme disease may not
appear until weeks, months, or years after a tick bite:

Arthritis is most likely to appear as brief bouts of pain and swelling,
usually in one or more large joints, especially the knees.

Nervous system abnormalities can include numbness, pain, Bell's palsy
(paralysis of the facial muscles, usually on one side), and meningitis
(fever, stiff neck, and severe headache).

Less frequently, irregularities of the heart rhythm occur.

In some persons the rash never forms; in some, the first and only sign
of Lyme disease is arthritis, and in others, nervous system problems
are the only evidence of Lyme disease.

Lyme disease and pregnancy

In rare cases, Lyme disease acquired during pregnancy may lead to
infection of the fetus and possibly to stillbirth, but adverse effects to
the fetus have not been conclusively documented. The Centers for Disease
Control and Prevention (CDC) maintains a registry of pregnant women with
Lyme disease to advance the understanding of the effects of Lyme disease on
the developing fetus.

Diagnosis

Lyme disease is often difficult to diagnose because its symptoms and
signs mimic those of many other diseases. The fever, muscle aches, and
fatigue of Lyme disease can easily be mistaken for viral infections, such
as influenza or infectious mononucleosis. Joint pain can be mistaken for
other types of arthritis, such as rheumatoid arthritis, and neurologic
signs can mimic those caused by other conditions, such as multiple
sclerosis. At the same time, other types of arthritis or neurologic
diseases can be misdiagnosed as Lyme disease.

Diagnosis of Lyme disease should take into account

History of possible exposure to ticks, especially in areas where Lyme
disease is known to occur.

Symptoms and signs.

The results of blood tests used to determine whether the patient has
antibodies to Lyme disease bacteria.

These tests are most useful in later stages of illness, but even then
they may give inaccurate results. Laboratory tests for Lyme disease have
not yet been standardized nationally.

Treatment and prognosis

Lyme disease is treated with antibiotics under the supervision of a
physician. Several antibiotics are effective. Antibiotics usually are given
by mouth but may be given intravenously in more severe cases. Patients
treated in the early stages with antibiotics usually recover rapidly and
completely. Most patients who are treated in later stages of the disease
also respond well to antibiotics. In a few patients who are treated for
Lyme disease, symptoms of persisting infection may continue or recur,
making additional antibiotic treatment necessary. Varying degrees of
permanent damage to joints or the nervous system can develop in patients
with late chronic Lyme disease. Typically these are patients in whom Lyme
disease was unrecognized in the early stages or for whom the initial
treatment was unsuccessful. Rare deaths from Lyme disease have been
reported.

Prevention

Tick Control: Removing leaves and clearing brush and tall grass around
houses and at the edges of gardens may reduce the numbers of ticks that
transmit Lyme disease. This is particularly important in the eastern United
States, where most transmission of Lyme disease is thought to occur near
the home.

A relationship has been observed between the abundance of deer and the
abundance of deer ticks in the eastern United States.

Applying acaricides (chemicals that are toxic to ticks) to gardens,
lawns, and the edge of woodlands near homes is being done in some areas,
but questions remain regarding its effectiveness and environmental safety.
Application to residential properties should be supervised by a licensed
professional pest control expert.

Reducing and managing deer populations in geographic areas where Lyme
disease occurs may reduce tick abundance. Removing plants that attract deer
and constructing physical barriers may help discourage deer from coming
near homes.

Personal protection from tick bites

The chances of being bitten by a tick can be decreased with a few
precautions.

Avoid tick-infested areas, especially in May, June, and July (many
local health departments and park or extension services have
information on the local distribution of ticks).

Wear light-colored clothing so that ticks can be spotted more easily.
Tuck pant legs into socks or boots and shirt into pants.

Tape the area where pants and socks meet so that ticks cannot crawl
under clothing.

Spray insect repellent containing DEET on clothes and on exposed skin
other than the face, or treat clothes (especially pants, socks, and
shoes) with permethrin, which kills ticks on contact.

Wear a hat and a long-sleeved shirt for added protection.

Walk in the center of trails to avoid overhanging grass and brush.

After being outdoors, remove clothing and wash and dry it at a high
temperature; inspect body carefully and remove attached ticks with
tweezers, grasping the tick as close to the skin surface as possible and
pulling straight back with a slow steady force; aviod crushing the tick's
body. In some areas, ticks (saved in a sealed container) can be submitted
to the local health department for identification.

Preventive Antibiotic Treatment: Antibiotic treatment to prevent Lyme
disease after a known tick bite may not be warranted. Physicians must
determine whether the advantages of using antibiotics outweigh the
disadvantages in any particular instance. If antibiotics are not used,
physicians should alert patients to the symptoms of early Lyme disease and
advise them to return for reevaluation if symptoms occur.

Lyme disease research

Research continues to discover

Where ticks are most likely to be and how best to protect against them.

Which chemicals and other approaches are best for controlling ticks in
each kind of habitat.

Better diagnostic tests.

Improved antibiotic treatment.

An effective vaccine.

Effects of mother's infection on the developing fetus.

How Lyme disease bacteria cause chronic infections of the joints and
nervous system and how to prevent these complications.

For further information, contact the CDC Voice Information System at
(404) 332-4555, your physician, or your local health department.

POINT OF CONTACT FOR THIS DOCUMENT:

To request a copy of this document or for questions concerning this
document, please contact the person or office listed below. If
requesting a document, please specify the complete name of the
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Note that if a name is listed with the address below, you may wish
to contact this person via CDC WONDER/PC e-mail.
CAROL D SNAREY
DIVISION OF VECTOR-BORNE INFECTIOUS DISEASES
Centers for Disease Control
1600 Clifton Rd, NE MS(C-14)
Atlanta, GA 30333

This page last reviewed:
Wednesday, January 27, 2016

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